Magnetic device to lift and melt a body without any holder



Jan. 9, 1968 M. NOIRET 3,363,081

MAGNETIC DEVICE TO LIFT AND MELT A BODY WITHOUT ANY HOLDER Filed Nov. 20, 1964 2 Sheets-Sheeil 1 FIG/I 2 R n VEYITOQ mam-ace. nolrejt By Paul), mlgfi' FFlToQnEy M. NOIRET Jan. 9, 1968 MAGNETIC DEVICE TO LIFT AND MELT A BODY WITHOUT ANY HOLDER Filed Nov. 20, 1964 2 Sheets-Sheet 2 t. Q e m P mm w m w. I w M 6 v l I f m.- ///mJ------ 56 United States Patent 3,363,081 MAGNETIC DEVICE T0 LIFT AND MELT A BODY WITHOUT ANY HOLDER Maurice Noiret, 3 Allee Traversiere, Fresnes, France Filed Nov. 20, 1964, Ser. No. 412,682 Claims priority, application France, Nov. 21, 1963,

16 Claims. (Cl. 21910.79)

ABSTRACT OF THE DISCLOSURE Magnetic device for the levitation and the fusion of an electrically conducting body comprising two cylindrical coils having the same horizontal axis and a cylindrical core made of conductive material located inside each coil.

It is known that when the melting of certain bodies is executed at a very high temperature, the melting pot or the holder on which rests the body may be affected during the melting process, and this brings about a pollution of the body. As a matter of fact, the superficial dilution of the holder resulting from the high temperature causes the impurities in the holder to penetrate the melted body when this latter is in its liquid state.

The present invention provides a remedy for these drawbacks. Its object is to provide a device allowing the fusion of an electrically conductive body under such conditions that no impurities can contaminate this body when it is in its liquid state. This device is characterized by the fact that the fusion of the body is realized under the action of the heat emitted by the eddy currents generated through the action of a high frequency electromagnetic intense field (designated in the following by magnetic field) said field serving also as a support for maintaining the body in a stable position of equilibrium without resort to use of a mechanical holder of any kind in contact with the body.

In order to insure that the position in which the body is placed under the action of a magnetic field is a position of stable equilibrium, it has been noted that the application point of the magnetic forces counter-acting the effect of the gravity forces on the body must be situated inside a volume or area in which the magnetic field passes through a point or region of minimum intensity. The magnetic field gradient in the whole region where the body is situated must also be negative so as to insure that the body will be properly supported. As a matter of fact, in accordance with the invention, the generated magnetic field is oriented such that the course or path of movement that the body would tend to take under the action of the force of gravity will cut lines of field of increasing intensities which are opposed to this displacement.

On the other hand, in order to operate a fusion under vacuum, it seems essential that the magnetic field which generates the eddy currents causing the temperature rise necessary to said fusion not possess a vertical symmetry axis'of revolution, so that the mechanical equilibrium of the bodies submitted to such a fusion are independent of the superficial tensions of said bodies when they are in the liquid state. The device according to the present invention provides for complete satisfaction of these two requirements.

Other advantages and particularities will appear from the description hereunder given as an illustrative and in no way limitative example of a preferential embodiment of the invention which is presented on the accompanying drawings.

FIGURE 1 shows a classical magnetic device of the invention and FIGURE 2 shows the curve of the distribution of the magnetic field in a determined plane.

FIGURES 3, 5 and 7 represent variations of the embodiment of the device according to the invention, the corresponding curves of the distribution of the magnetic field generated by said device in a determined plane being illustrated by FIGURES 4, 6, 8.

FIGURE 9 shows a conventional cooling system utilized with the invention.

FIGURE 10 is a section along line X-X in FIG- URE 7.

In FIGURE 1 are shown two cylindrical coils schematically represented by their windings 1 and 2 and placed along a common horizontal axis A. A body 3 for example, constituted by a conductive material, is placed on the axis A, at equal distances from the coils 1 and 2. When a current flows through the coils 1 and 2, a magnetic field appears, the lines of force of which are represented in 4. If one investigates the distribution of the field so created in the symmetry plane of the device, one knows that the field is maximum at the point C which is the intersection of the axis A and of the trace D of the above mentioned symmetry plane. The variations of the magnetic induction B as a function of the radial distance R are represented in FIGURE 2. As can be seen, this induction is maximum at the point C and decreases as the distance from the axis A increases. A solid spherical body, the center of which coincides with the point C is therefore in a position of unstable equilibrium since it is subjected to the force of gravity but not to any electrically originated force tending to oppose gravity however, as soon as its center swerves from the point C, the forces due to the magnetic field tend to force it back to point C, because, as is well known, a body tends to place itself in a position where it embraces a minimum flux.

The device according to the invention shown in FIG- URE 3 makes it possible to obtain a magnetic field, the outline of which, in the space, does not have a vertical axis of revolution, and the intensity of which presents a minimum at point C. As a result, the point C is in a position of stable equilibrium for a spherical body, the center of which is placed in the immediate vicinity of this point. The device comprises two coils schematically represented by their windings 1 and 2 and a core including two elements 5 and 5' constituted of a conductive material, for example, copper cooled by liquid circulation. The axis of the field coincides with the axis of the coils 1 and 2, which behave like a diamagnetic body I when submitted to a high frequency magnetic field.

The coils 1 and 2 are supplied with a high frequency alternating current, such that the field lines crossing the core 5 concentrate on the core periphery and one observes a certain pinching of the, field lines 4. The point C corresponds to a minimum field, the variation of this latter being represented on FIGURE 4.

In another embodiment according to the invention, shown in FIGURE 5, the core is placed above the symmetry axis A of the coils 1 and 2. The minimum magnetic field is then no longer found at the point C but is positioned above this point, as shown in FIGURE 6. The position of the body 3 is however a position of stable equilibrium, the curve on FIGURE 6 showing that the forces exerted by the magnetic field on the body 3 push the body upwards with a force sufficient to oppose the opposite forces due to gravity. 7

FIGURE 7 represents another embodiment according to the invention in which the coils 1 and 2 include a field concentrator constituted by a cylinder having two parts 6 and 6 made of conductive metal, the cylinder being split, as seen in FIGURE 10, along one of its generating lines. Inside the cylinder are set the cores 5 and 5 tangentially to the internal surface of the cylinder parts 6 and 6'. The result of this disposition is the alteration of the distribution curve of the field, shown in FIGURE 8, the decrease of the field being steeper as the distance from the axis A increases. The field concentrator 6 is cooled in a conventional manner by liquid circulation as indicated below with reference to FIGURE 9.

FIGURE 9, illustrates, by way of example, one conventional means for cooling the cores 5 and 5' (illustrated with respect to the core 5 only). As seen in the figure the core 5 is provided in the form of a hollow finger 51 having a thickness greater than that affected by the skin-effect of the magnetic field. The core 5 is provided with a cavity 52 where a cooling liquid, for example water, may circulate. The cavity '52 is closed by a copper disc 54 which may be soldered into the opening or recess 53 and a pair of pipes 55 and 56 extend through the disc 54 for distributing the cooling water to and from the cavity in accordance with the arrows in the figure.

The extremities of the pole-pieces of the coils 1 and 2 constituted by the cores 5 and 5 may be plane or have the shape of a portion of a sphere with a diameter equal to or greater than that of the cores 5 and 5. The different shapes of said extremities depending on the nature of the body which is intended to be lifted and melted, the pole shoe of the pole pieces allowing a higher concentration of the field.

In the case of the bodies for which it is advantageous to execute the fusion under vacuum, the above described device is placed in a leak proof enclosure, not represented in the figures, which is brought up to a high degree of vacuum.

Of course, one can bring different variants and modifications to the above described embodiments given only as illustrative examples without departing from the scope of the invention.

What I claim is:

1. In a device for holding and melting a body of electrically conductive material without effecting physical contact with said body comprising coil means generating a high frequency magnetic field including a pair of coils positioned substantially coaxially with a horizontal axis, and

core means including a core member placed in the inner magnetic field within each of said coils, said core members being made of an electrically conductive material having a diamagnetic behavior upon the action of a high frequency magnetic field, said coils and said core members being respectively positioned symmetrically with respect to a common vertical plane defining a minimum magnetic field region situated outside of each of said coils.

2. A magnetic device as defined in claim 1 wherein said core members have a substantially elongated shape.

3. A magnetic device according to claim 2 wherein said core members have a common axis of symmetry coinciding with the horizontal axis of said coils.

4. A magnetic device according to claim 1 wherein said core members have a common axis of symmetry parallel to and offset from the axis of said coils in a direction opposite to that of gravity.

5. A device according to claim 1 including field concentrators having a substantially hollow cylindrical shape, positioned at the inner part of said coils and coaxial therewith and surrounding said core members, said concentrators being made of an electrically conductive material.

6. A device according to claim 1 wherein the facing extremities of said core members are planar.

7. A device according to claim 1 wherein the facing extremities of said core members have a partially spherical shape.

8. A device according to claim 1 wherein said core members include cooling means for effecting cooling thereof.

9. A device according to claim 5 wherein said concentrator includes cooling means for effecting cooling thereof.

10. A device according to claim 5 comprising leakproof housing means and pumping means for establishing a high degree of vacuum in said housing means.

11. A device according to claim 5 wherein said core members are positioned adjacent to the inner surface of said field concentrations.

12. In a device for melting a body of electrically conductive material, the improvement essentially consisting of means for holding and heating said body without effecting physical contact therewith comprising coil means generating a high frequency magnetic field including a pair of spaced substantially co-axial coils having a common horizontal axis, and

a body of conductive material to be melted positioned at the point of intersection of a plane of symmetry passing between said pair of coils and being transverse to the axis of said coils,

core means including individual conductive core mem bers placed within each of said coils in spaced relationship Within the magnetic field thereof so as to have a diamagnetic effect upon the action of said high frequency magnetic field.

13. In a device for melting a body of electrically conductive material, the improvement essentially consisting of means for holding and heating said body without effecting physical contact therewith comprising coil means generating a high frequency magnetic field A including a pair of substantially co-axial coils, and a body of conductive material to be melted positioned at the point of intersection of a plane of symmetry passing between said pair of coils and being transverse to the axis of said coils having a common horizontal axis, core means including individual conductive core members placed within each of said coils within the magnetic field thereof so as to have a diamagnetic efiect ifilpltzin the action of said high frequency magnetic e said core means being offset with respect to the axis of said coil means so as to provide a non-symmetrical magnetic field within the area of said body. 14. In a device for melting a body of electrically conductive material, the improvement essentially consisting of means for holding and heating said body without effecting physical contact therewith comprising coil means generating a high frequency magnetic field including a pair of substantially co-axial coils having a common horizontal axis, and core means including individual conductive core members placed within each of said coils within the magnetic field thereof so as to have a diamagnetic effect upon the action of said high frequency magnetic field. 15. In 'a device for melting a body of electrically conductive material, the improvement essentially consisting of means for holding and heating said body without effecting physical contact therewith comprising coil means generating a high frequency magnetic field including a pair of substantially co-axial coils having a common horizontal axis, and core means including individual conductive core members placed within each of said coils within the magnetic field thereof so as to have a diamagnetic effect upon the action of said high frequency magnetic field, said core means being offset with respect to the axis of said coil means so as to provide a non-symmetrical magnetic field within the area of said body.

References Cited UNITED STATES PATENTS 2,664,496 12/1953 Brace 13-26 2,686,864 8/1954 Wroughton et a1. 219-7.5 2,957,064 10/1960 Comentz 21910.49

6 FOREIGN PATENTS 567,268 12/1958 Canada.

622,023 4/1949 Great Britain.

RICHARD M. WOOD, Primary Examiner.

L. H. BEN DER, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATEQ]; CORRECTION Patent No. 3,363,081 January 9, 1968 Maurice Noiret It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

1 n the heading to the printed specification, line 4 "3 Allee 1%" rsiere, Fresnes France" should read Fresnes France,

aseignor to Compagnie Generale d'Electricite, Paris, France,

a corporation of France :34

Signed and sealed this fi'th day of January 1970.

M. Fletcher, Jr. WILLIAM E.

Commissioner of Patents Attesting Officer 

